More recent developments in surgery and/or orthopedics have led to the design of prosthetic femoral caps for which, when they are inserted into the body of a patient, only the surface and/or exterior layer of the femoral head (caput femoris) is removed and replaced with a metal cap. This method for removing the surface of the bone (“resurfacing”) differs from the conventional methods in that the femoral head has hitherto been simply sawn off and replaced entirely with a prosthetic shaft. Resurfacing has hitherto been completed manually, i.e. the apparatus for removing—in particular, fraising off—the surface of the bone has been manually guided by a surgeon, wherein this has resulted in major uncertainties due to a movement of the fraising drill relative to the femur.
When fraising the surface of the bone in the hitherto usual way, so-called “femoral notching” has occurred: by manually guiding the fraising head, it is possible to inadvertently fraise a notch into the femoral neck, which can lead to a fracture of the femoral neck when a load is post-operatively placed on the hip joint.